TPX™ (Polymethylpentene or PMP) is a heat resistant multi-function polymer, from Mitsui Chemicals Inc. (MCI), produced through the polymerization of the polypropylene dimer. It is one of the lightest polymer materials among thermoplastics currently available for commercial use. TPX™ has a characteristic helical structure, with a bulky side chain, that gives it some very useful properties.